You could enforce a redirect via cPanel.
As far of registration goes, you could disable registration by creating an empty registration view in a plugin, or deactivate the registration.
This plugin should work also on Elgg 1.6 to disable registrations: http://community.elgg.org/plugins/462753/1/turn-off-elgg-registrations.
You might also think about upgrading your site to Elgg 1.7 and then 1.8. On Elgg 1.8 there's a built-in option to disable registrations. If you would upgrade your site, you would close all the many security issues that were identified and fixed since Elgg 1.6 (the spam might not only be posted on your site by creation of regular accounts but also by exploitation of unfixed security issues).
The effort necessary to upgrade your site depends on which plugins your are using on your site. If you are not using any 3rd party plugins / a theme plugin, the upgrade shouldn't be complicated at all as there shouldn't be any compatibility issues on upgrading. If you are using 3rd party plugins, you can check if there are new releases available for Elgg 1.7 / Elgg 1.8. If yes, there's no problem with upgrading your site either. If not, you might think about upgrading your site nonetheless but stop using these particular plugins.
Thank you very much indeed lionly! The Webgalli disable registrations plugin worked a treat.
MUCH APPRECIATED!
And do consider upgrading. It's tough, I know, but you reap so many benefits in performance and security and support.
If the server allows it (I know some do) you could set PHP version to less than 5.4 only for the elgg site.
However, 1.6 is outdated and no longer supported, you must consider upgrading to 1.7.x
If you do make the decision to upgrade, you might as well skip 1.7 as it will be obsolete very soon...
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